Kiss Me, Kill Me book by Allison Brennan

Lucy Kincaid has firsthand experience dealing with deadly criminal predators, and she’s fully prepared to share her many talents with the FBI. But when her career plans are derailed, her boyfriend, security expert Sean Rogan, asks for help on his latest private investigation. Using her well-honed cyber-hunting skills, Lucy is soon on the trail of a missing teenage girl with a penchant for disappearing—and a shocking secret life.

FBI Agent Suzanne Madeaux is also tracking a serial killer on the loose in New York City. Dubbed by the press the Cinderella Strangler, he cruises seamy underground sex parties, where drug-fueled women make for easy pickings. As Lucy and Sean’s desperate search collides with the FBI’s hunt, Lucy isn’t about to step aside. Haunted by painful memories of her own harrowing encounters with evil, she’s determined to keep any more innocents from meeting the fate she so narrowly escaped. Delving deep into the twisted psyche of a remorseless killer, Lucy must confront her own fears—even if it means risking a future job with the FBI and future happiness with Sean.